To solve problems that are a reduction in environmental load to deal with a global greenhouse gas emissions-reduction problem and an increase in fuel price, in recent years, there is a need for an improvement of energy saving of ships and their operations in shipbuilding and shipping industries. In addition, research developments regarding the maintenances and improvements of the safety of the sail of the ships and the transportation quality have been accelerated. In accordance with such a trend, the importance of an optimal seafaring technology, called weather routing, is increasing. The weather routing is a seafaring technology which predicts an encounter marine phenomenon in a marine area, in which a ship sails, based on marine phenomenon states and accumulated marine phenomenon information and proposes an optimal planned route (minimum-time route) for the purpose of minimizing the fuel consumption and securing the safety and the punctuality.
To reduce the fuel consumption of the sail of the ship, it is desirable to select a route along which the ship can sail at the lowest possible power output and to set the revolution of a main engine in that manner. However, the optimal planned route proposed by the current weather routing prioritizes the reduction in sail time, and the reduction in the fuel consumption by the reduction in the sail time is targeted. Therefore, the sail along this optimal planned route is not necessarily economical sail by which the fuel consumption is reduced. The optimal planned route proposed by the current weather routing is calculated based on meteorological and marine phenomena prediction information acquired at long-time intervals, such as at one-day intervals. To be specific, the current weather routing does not consider, for example, the meteorological and marine phenomena which change as the ship sails along the route or the meteorological and marine phenomena which have changed in a short period of time. Therefore, the optimal planned route proposed by the current weather routing is not necessarily a route in which the meteorological and marine phenomena of the current position of the ship and the current state of the ship are reflected. Due to the above reasons, in actual ship maneuvering sites, the ship leaves the optimal planned route proposed by the weather routing, and the ship maneuvering, such as a change in course or an adjustment of the ship speed, is performed based on experience and intuition of a ship pilot in accordance with actually encountered meteorological and marine phenomena. Problems of this ship maneuvering are that the ship pilot feels burdens, and determinations vary among the ship pilots.
Various proposals to conduct economically optimal sail have been made. For example, PTL 1 discloses an integrated navigation device. The integrated navigation device is configured to: calculate a most energy saving route from a departure place to a destination based on meteorological and marine phenomena data of respective marine areas and respective seasons and a current state and forecast data distributed from, for example, a communications satellite; and automatically sail along the most energy saving route by the combination of autopilot and a main engine control system.
For example, PTL 2 discloses an optimal route search method. When calculating an optimal route from a departure point to a destination in a marine area based on ship performance data specific to each ship and a forecast value of marine and meteorological phenomena data indicating long-term marine and meteorological phenomena states, the optimal route search method uses the forecast value of the marine and meteorological phenomena data, which changes temporally and spatially at the calculated position of the ship, each time a certain period of time elapses until the ship reaches the destination.